People were (rightly) critical of the notion that missile defense was something the United States could rely upon to survive a nuclear war. Scientists pointed

People were (rightly) critical of the notion that missile defense was something the United States could rely upon to survive a nuclear war. Scientists pointed out that this is a dangerous strategy, and that non-proliferation and arms reduction treaties were the only sane way to avoid nuclear annihilation. There is no amount of technology that is going to save Europe and the US in an all out nuclear war. Theatre missile defense is another story. Systems like the S-400, the Patriot missile system and David's Sling can quite effectively protect a region from a variety of conventional aerial threats. They have been dutifully doing their job since the 1990s and are improving.